Question

我在几秒钟后添加了一个关闭UIAlertView的函数。整个代码如下：


- (void)netWorkAlert
{
    UIAlertView *netWork = [[UIAlertView alloc] initWithTitle:@"error" message:@"network has problems" delegate:self cancelButtonTitle:nil otherButtonTitles: nil];
    [netWork show];
    [self performSelector:@selector(dismissAlert:) withObject:netWork afterDelay:2];
}
- (void)dismissAlert:(UIAlertView *)alert
{
    if(alert)
    {
        [alert dismissWithClickedButtonIndex:0 animated:YES];
        [alert release];
    }
}

当网络不可用时调用netWorkAlert。

现在我遇到的问题是第二次调用netWorkAlert时，应用程序被破坏，Xcode显示错误


int main(int argc, char *argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([ZJAppDelegate class]));
//Thread 1 :EXC_BAD_ACCESS(code=1,address=xc0000004)
    }
}

我没有使用ARC，我不知道为什么会崩溃。即使我对[alert release];发表评论，它仍然会在第二次出现同样的问题。

有人可以帮我查一下吗？谢谢！

Answer 1

EXC_BAD_ACCESS是由访问已发布的对象引起的。为了避免这种情况，请调用UIAlertView类型的模式：

功能体：

-(void)checkSaving
{
    UIAlertView *alert = [[UIAlertView alloc]
        initWithTitle:@"Do you want to add these results to your database?"
        message:@"\n\n"
        delegate:self
        cancelButtonTitle:@"No"
        otherButtonTitles:@"Save", nil];
    alert.alertViewStyle = UIAlertViewStyleDefault;
    [alert show];
    //this prevent the ARC to clean up :
    NSRunLoop *rl = [NSRunLoop currentRunLoop];
    NSDate *d;
    d= (NSDate*)[d init];
    while ([alert isVisible]) {
        [rl runUntilDate:d];
    }

}

您的选择结果：

- (void)alertView:(UIAlertView *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
    // the user clicked one of the OK/Cancel buttons
    if (buttonIndex == 1)//Save
    {
        //do something

    }
    if (buttonIndex == 0)//NO
    {
        //do something
    }
}

在接口声明中注册函数：

@interface yourViewController ()
    -(void)checkSaving
    - (void)alertView:(UIAlertView *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
//...
@end

致电： [self checkSaving];

我希望这会对你有帮助。

Answer 2

在调用dismissAlert方法时，UIAlertView可能超出范围（对alert nil的检查会阻止此代码崩溃。但是，有一个更好的方法实现这一点的方法alert永远不会超出范围。

定义networkAlert方法的类应该实现<UIAlertViewDelegate>协议。下面的代码允许您拦截用户单击“取消”按钮并执行自定义操作。按取消的默认操作是关闭UIAlertView。

@interface YourClassName : UIViewController <UIAlertViewDelegate> {}

@implementation YourClassName

-(void) networkAlert
{
    UIAlertView *netWork = [[UIAlertView alloc] initWithTitle:@"error" 
                                                      message:@"network has problems"
                                                     delegate:self 
                                            cancelButtonTitle:@"cancel" 
                                            otherButtonTitles:nil];
    [netWork show];
}

- (void) alertViewCancel:(UIAlertView*)alertView 
{
    what ever it is you want to do when the cancel button is pressed here
}

UIAlertview exc_bad_access

2 个答案: